[syzbot] KASAN: use-after-free Read in __kernfs_remove

From: syzbot
Date: Thu Aug 25 2022 - 14:25:44 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 68a00424bf69 Add linux-next specific files for 20220824
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10cedc45080000
kernel config: https://syzkaller.appspot.com/x/.config?x=591008a24ae652d0
dashboard link: https://syzkaller.appspot.com/bug?extid=8bee3285b9e190f1509e
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123a6fb5080000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15381113080000

The issue was bisected to:

commit b10b85fe5149ee8b39fbbf86095b303632dde2cd
Author: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Date: Wed Jul 27 14:31:30 2022 +0000

ovl: warn if trusted xattr creation fails

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=126b3c65080000
final oops: https://syzkaller.appspot.com/x/report.txt?x=116b3c65080000
console output: https://syzkaller.appspot.com/x/log.txt?x=166b3c65080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8bee3285b9e190f1509e@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: b10b85fe5149 ("ovl: warn if trusted xattr creation fails")

==================================================================
BUG: KASAN: use-after-free in kernfs_type include/linux/kernfs.h:335 [inline]
BUG: KASAN: use-after-free in kernfs_leftmost_descendant fs/kernfs/dir.c:1261 [inline]
BUG: KASAN: use-after-free in __kernfs_remove+0xa09/0xb50 fs/kernfs/dir.c:1369
Read of size 2 at addr ffff8880175239a8 by task syz-executor325/4044

CPU: 1 PID: 4044 Comm: syz-executor325 Not tainted 6.0.0-rc2-next-20220824-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
print_address_description mm/kasan/report.c:317 [inline]
print_report.cold+0x2ba/0x719 mm/kasan/report.c:433
kasan_report+0xb1/0x1e0 mm/kasan/report.c:495
kernfs_type include/linux/kernfs.h:335 [inline]
kernfs_leftmost_descendant fs/kernfs/dir.c:1261 [inline]
__kernfs_remove+0xa09/0xb50 fs/kernfs/dir.c:1369
kernfs_remove_by_name_ns+0xa8/0x110 fs/kernfs/dir.c:1589
sysfs_slab_add+0x13e/0x1e0 mm/slub.c:5756
__kmem_cache_create+0x509/0x690 mm/slub.c:4745
create_cache mm/slab_common.c:229 [inline]
kmem_cache_create_usercopy+0x1f9/0x300 mm/slab_common.c:335
p9_client_create+0xca5/0x1070 net/9p/client.c:993
v9fs_session_init+0x1e2/0x1810 fs/9p/v9fs.c:408
v9fs_mount+0xba/0xc90 fs/9p/vfs_super.c:126
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1530
do_new_mount fs/namespace.c:3040 [inline]
path_mount+0x1326/0x1e20 fs/namespace.c:3370
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9adb816389
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 14 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff4b66cf98 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff4b66cfd0 RCX: 00007f9adb816389
RDX: 0000000020000280 RSI: 00000000200002c0 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000020000140 R09: 000000000000c837
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000000f4240
R13: 000000000000c837 R14: 00007fff4b66cfbc R15: 00007fff4b66cfc0
</TASK>

Allocated by task 4039:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track mm/kasan/common.c:45 [inline]
set_alloc_info mm/kasan/common.c:437 [inline]
__kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:470
kasan_slab_alloc include/linux/kasan.h:224 [inline]
slab_post_alloc_hook mm/slab.h:737 [inline]
slab_alloc_node mm/slub.c:3229 [inline]
slab_alloc mm/slub.c:3237 [inline]
__kmem_cache_alloc_lru mm/slub.c:3244 [inline]
kmem_cache_alloc+0x2b7/0x3d0 mm/slub.c:3253
kmem_cache_zalloc include/linux/slab.h:685 [inline]
__kernfs_new_node+0xd4/0x8b0 fs/kernfs/dir.c:593
kernfs_new_node fs/kernfs/dir.c:655 [inline]
kernfs_create_dir_ns+0x9c/0x220 fs/kernfs/dir.c:1010
sysfs_create_dir_ns+0x127/0x290 fs/sysfs/dir.c:59
create_dir lib/kobject.c:63 [inline]
kobject_add_internal+0x2c9/0x8f0 lib/kobject.c:223
kobject_add_varg lib/kobject.c:358 [inline]
kobject_init_and_add+0x101/0x160 lib/kobject.c:441
sysfs_slab_add+0x161/0x1e0 mm/slub.c:5767
__kmem_cache_create+0x509/0x690 mm/slub.c:4745
create_cache mm/slab_common.c:229 [inline]
kmem_cache_create_usercopy+0x1f9/0x300 mm/slab_common.c:335
p9_client_create+0xca5/0x1070 net/9p/client.c:993
v9fs_session_init+0x1e2/0x1810 fs/9p/v9fs.c:408
v9fs_mount+0xba/0xc90 fs/9p/vfs_super.c:126
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1530
do_new_mount fs/namespace.c:3040 [inline]
path_mount+0x1326/0x1e20 fs/namespace.c:3370
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

Freed by task 4044:
kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
kasan_set_track+0x21/0x30 mm/kasan/common.c:45
kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
____kasan_slab_free mm/kasan/common.c:367 [inline]
____kasan_slab_free+0x166/0x1c0 mm/kasan/common.c:329
kasan_slab_free include/linux/kasan.h:200 [inline]
slab_free_hook mm/slub.c:1740 [inline]
slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1766
slab_free mm/slub.c:3497 [inline]
kmem_cache_free+0xe7/0x5b0 mm/slub.c:3519
kernfs_put.part.0+0x2c4/0x540 fs/kernfs/dir.c:547
kernfs_put+0x42/0x50 fs/kernfs/dir.c:521
__kernfs_remove+0x7a6/0xb50 fs/kernfs/dir.c:1407
kernfs_remove_by_name_ns+0xa8/0x110 fs/kernfs/dir.c:1589
sysfs_slab_add+0x13e/0x1e0 mm/slub.c:5756
__kmem_cache_create+0x509/0x690 mm/slub.c:4745
create_cache mm/slab_common.c:229 [inline]
kmem_cache_create_usercopy+0x1f9/0x300 mm/slab_common.c:335
p9_client_create+0xca5/0x1070 net/9p/client.c:993
v9fs_session_init+0x1e2/0x1810 fs/9p/v9fs.c:408
v9fs_mount+0xba/0xc90 fs/9p/vfs_super.c:126
legacy_get_tree+0x105/0x220 fs/fs_context.c:610
vfs_get_tree+0x89/0x2f0 fs/super.c:1530
do_new_mount fs/namespace.c:3040 [inline]
path_mount+0x1326/0x1e20 fs/namespace.c:3370
do_mount fs/namespace.c:3383 [inline]
__do_sys_mount fs/namespace.c:3591 [inline]
__se_sys_mount fs/namespace.c:3568 [inline]
__x64_sys_mount+0x27f/0x300 fs/namespace.c:3568
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

The buggy address belongs to the object at ffff888017523910
which belongs to the cache kernfs_node_cache of size 168
The buggy address is located 152 bytes inside of
168-byte region [ffff888017523910, ffff8880175239b8)

The buggy address belongs to the physical page:
page:ffffea00005d48c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888017523570 pfn:0x17523
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea00005d4c80 dead000000000006 ffff8880119d4c80
raw: ffff888017523570 000000008011000b 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x12cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY), pid 1, tgid 1 (swapper/0), ts 2122740088, free_ts 0
prep_new_page mm/page_alloc.c:2532 [inline]
get_page_from_freelist+0x109b/0x2ce0 mm/page_alloc.c:4283
__alloc_pages+0x1c7/0x510 mm/page_alloc.c:5507
alloc_page_interleave+0x1e/0x200 mm/mempolicy.c:2113
alloc_pages+0x22f/0x270 mm/mempolicy.c:2275
alloc_slab_page mm/slub.c:1810 [inline]
allocate_slab+0x27e/0x3d0 mm/slub.c:1955
new_slab mm/slub.c:2015 [inline]
___slab_alloc+0xa3e/0x11d0 mm/slub.c:3017
__slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3104
slab_alloc_node mm/slub.c:3195 [inline]
slab_alloc mm/slub.c:3237 [inline]
__kmem_cache_alloc_lru mm/slub.c:3244 [inline]
kmem_cache_alloc+0x31c/0x3d0 mm/slub.c:3253
kmem_cache_zalloc include/linux/slab.h:685 [inline]
__kernfs_new_node+0xd4/0x8b0 fs/kernfs/dir.c:593
kernfs_new_node fs/kernfs/dir.c:655 [inline]
kernfs_create_dir_ns+0x9c/0x220 fs/kernfs/dir.c:1010
internal_create_group+0x787/0xb10 fs/sysfs/group.c:136
kernel_add_sysfs_param kernel/params.c:814 [inline]
param_sysfs_builtin kernel/params.c:851 [inline]
param_sysfs_init+0x342/0x43b kernel/params.c:970
do_one_initcall+0xfe/0x650 init/main.c:1301
do_initcall_level init/main.c:1376 [inline]
do_initcalls init/main.c:1392 [inline]
do_basic_setup init/main.c:1411 [inline]
kernel_init_freeable+0x6b1/0x73a init/main.c:1630
kernel_init+0x1a/0x1d0 init/main.c:1519
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
page_owner free stack trace missing

Memory state around the buggy address:
ffff888017523880: fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc fc
ffff888017523900: fc fc fa fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888017523980: fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc fa
^
ffff888017523a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff888017523a80: fb fb fb fb fc fc fc fc fc fc fc fc fa fb fb fb
==================================================================

---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx.

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For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

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